Passive devices which have electrical dimensions comparable with the working wavelength, and which operate at frequencies up to but not including optical frequencies, e.g. microwave, and their manufacture.

In this place, the following terms or expressions are used with the meaning indicated:

Auxiliary devices

Devices which perform an operation other than the mere simple transmission of energy.

Waveguide type

As applied to transmission lines, this term includes only high-frequency coaxial cables or Lecher lines, and as applied to resonators, delay lines, or other devices, this term includes all devices having distributed inductance and capacitance.

Synonyms and Keywords

In patent documents, the following abbreviations are often used:

Non-reciprocal devices

Components such as circulators or isolators, using the propagation properties of ferrites.

{the energy being transmitted in at least one ring-shaped transmission line located around the axis of rotation, e.g. "around the mast" rotary joint (H01P 1/069 takes precedence; coaxial line with solid inner conductor H01P 1/067)}

Aperture in a waveguide to insulate microwave circuits from differential pressures, but they enable the propagation of microwaves without introducing reflection or internal resonance.

Windows of the kind which serve to isolate the environment without a section of electromagnetic transmission line from another environment of different pressures and/or other environmental conditions, and which allow electromagnetic energy travelling along the transmission line to pass through the window with little or no loss of power.

Anisotropic media: Media where the vectors E and D are nonparallel and/or nonparallel H and B vectors, which means that the media has different electrical properties in different directions, and thus the permittivity and/or permeability has a matrix form.

Ferrites are ferromagnetic ceramic materials, compounds of iron, boron and barium or strontium or molybdenum. Ferrites have a high magnetic permeability, which allows them to store stronger magnetic fields than iron, and are known as ceramic magnets.

Applying a DC magnetic bias field to a ferrite will produce that a microwave signal will propagate differently in different directions, this effect can be utilized to fabricate directional devices as isolators, circulators and gyrators. The interaction with an applied microwave signal can be controlled by adjusting the strength of the bias field, which leads to a variety of control devices such as phase shifters, switches and tunable resonators and filters.

Faraday rotation is the rotation of the plane of polarization of microwave energy exhibited when the energy is transmitted through ferrite material in the direction of a magnetic field.

A ferrite rod is included within the waveguide and is usually surrounded by an electrical coil to provide a magnetic field. By adjusting the plane of polarisation of the microwave radiation, its propagation along the waveguide may be controlled.

This classification is very general, only related to filters that can not be clearly included in any of the following classifications or to theoretic articles/application where no specific filter arrangement (microstrip, stripline, waveguide, coaxial, coplanar, etc...) has been specified.

Bandpass or band-pass filters.

Low-pass or lowpass filters.

High-pass or highpass filters

References

Limiting references

This place does not cover:

If the application is more focussed in the material of the substrate and it is, in particular, a METAMATERIAL.

The NRD guide circuit (Non-radiative dielectric waveguide) has a structure with a dielectric line through which an electromagnetic wave is transmitted and it is sandwiched between two parallel conductive plates made from conductive metal. A space of the two parallel plates is less than half a free space wavelength of a using frequency. Accordingly, the electromagnetic wave is blocked in plates other than the dielectric line and its radiation is restricted, so that the NPD guide circuit can transmit the electromagnetic wave along the dielectic line at a small loss.

A structure that possesses a dispersion relation having a bandgap in which propagation of electromagnetic waves is prohibited in a specified frequency band is called an electromagnetic bandgap structure.

A photonic bandgap structure is a periodic arrangement of "defects" (e.g., pits or holes formed in layer of a device) that prevents the propagation of all electromagnetic waves within a particular frequency band. The defects introduce electrical frequency stop-bands much like a Bragg grating or crystal lattice structure introduces stop-bands in an optical transmission system. The spacing of the photonic bandgap structure's periodic defects determines the stop-band frequencies.

An electromagnetic bandgap* structure (EBG) is recently receiving attention as a scheme to solve some noise problems in microwave applications. This is for the purpose of blocking a signal ranging a certain frequency band by arranging the EBG having a certain structure in a printed circuit board, and the typical EBG has roughly two, namely a Mushroom type EBG(MT-EBG) and a Planar type EBG(PT-EBG).

* To have a better explanation of the electromagnetic bandgaps, see XP11037787, XP1034579

This EBG structure functions as a magnetic wall that reflects incident electromagnetic waves in phase in the vicinity of the band gap frequency band. For this reason, by installing the EBG structure on the back surface of an antenna, it is possible to achieve a lower profile of the antenna while maintaining its radiation efficiency.

The metamaterial is an artificial substance having an electromagnetic or optical characteristic which is not provided in substances existing in the natural world. Representative characteristics of such a metamaterial include negative magnetic permeability ([mu]<0), negative dielectric constant ([element of]<0), or negative refractive index (in a case where both of the magnetic permeability and the dielectric constant are negative).

Glossary of terms

In this place, the following terms or expressions are used with the meaning indicated:

combining or separating two or more different frequencies (H01P 1/215 takes precedence)

Definition statement

This place covers:

One input frequency is divided in several output frequencies (2 or more)

A multiplexer is a network that separates signals from a common port to other ports, sorted according to their frequency. A diplexer is a pair of filters arranged in a three port network, such that a signal at port one will be delivered to port 2 if it is a certain frequency band, and delivered to port 3 if it is in another frequency band.

Duplexer is the term used in radar for the element which separates transmitter and receiver (Section 1.3 Skolnik). However, in the patent literature both terms (diplexer and duplexer) are sometimes confused.

Hybrid arrangements, i.e. for transition from single-path two-way transmission to single transmission on each of two path, or vice-versa (multiport networks H03H 7/46; microwave multiplexers H01P 1/213)

An evanescent mode waveguide may have a conducting tube having an arbitrary cross-sectional shape and having at least one resonator. The dimensions of the cross-section are chosen to allow wave propagation at the operating frequency of interest while causing other frequencies to rapidly decay. A sectional length of an evanescent mode waveguide can be represented as a pi or tee section of inductors whose values are functions of section length, dielectric constant, and guide cross section. A resonant post may be inserted in such a way that it penetrates the broad wall of the evanescent mode waveguide, thereby forming a shunt capacitive element between opposite conducting walls of the guide. The resulting combination of shunt inductance and shunt capacitance forms a resonance.

Evanescent resonators are typically constructed from lengths of below-cutoff (e.g. dispersive) transmission line with the resonators formed by posts, capacitive screws, ridges.

An edge-guided mode device is provided with a dominant mode that resembles TEM energy propagation except that there is a strong transverse field displacement causing the wave energy to be concentrated along the edges of a metal stripline conductor formed on the surface of a ferrite substrate located on a metal ground plane and having a magnetic field applied thereto perpendicular to the ground plane. The edges are designed to be free of abrupt changes in order that there be no abrupt impedance change of the circuit. Non-reciprocal behaviour is obtained by asymmetrically loading the edges.

In this class of isolator, an absorption element (dummy load, dielectric member, ferrite slab, etc...) could be coupled to the isolator in order to absorb the energy of a microwave propagating backwardly.

Ferrite circulators are typically configured as multi-port (e.g., three-port) passive RF or microwave devices having within a housing magnets and ferrite material that may be used to control the direction of signal flow in, for example, an RF circuit or a microwave circuit. For example, ferrite circulators may be used to control signal flow in wireless base station or power amplifier applications. Ferrite isolators (see H01P 1/36) also may be constructed by terminating one port of a ferrite circulator. Terminating one port results in signal or energy flow in only one direction, which may be used, for example, for isolating components in a chain of interconnected components.

For more general information about circulators/isolators: http://www.tscm.com/circulat.pdf

The Faraday effect is produced when the plane of polarization of incident energy is rotated by passing the energy through an axially oriented, unidirectional, bias magnetic field. This principle is combined with well-known wave-guide principles in determining the propagation paths of electromagnetic energy in the coupler.

"Waveguide" as applied to transmission lines includes only high-frequency coaxial cables or Lecher lines, and as applied to resonators, delay lines, or other devices includes all devices having distributed inductance and capacitance.

The difference between a coplanar stripline and a coplanar line/waveguide is that the coplanar stripline has, at least 2, strip line conductors provided on a substrate and without ground electrodes between them.

Glossary of terms

In this place, the following terms or expressions are used with the meaning indicated:

A transmission line circuit is provided in which a layer of material is deposited on a conductive plane. Channels are formed (e.g., by etching) in material such that conductive plane is exposed. Signal traces are formed on a substrate (e.g., by etching the desired pattern in a copper sheet bonded to the substrate) which is then bonded to material such that traces are aligned with channels.

Proposed by Yoneyama and Nishida in 1981, non-radiative (NRD) guide circuit is nowadays a well-known technology for millimeter-wave applications. Its basic component, the NRD waveguide, consists of a rectangular section dielectric rod (height α, width 2w, permittivity εr), sandwiched between conductiong plates that are at a distance apart less than half the free space wavelength λ0: thus, all discontinuities that maintain appropriate symmetry become purely reactive, with the advantage of a strong reduction in interference and radiation problems in integrated circuits. The same waveguiding structure, but with a larger space between the plates, was already proposed in 1953 by Tischer with a view to obtaining an ultra-low-loss waveguide, know as H guide. In this situation the non radiation condition α < λ0/2 is no linger maintained and the structure suffers the drawback of undesirable radiation effects from discontinuities.

See GB2360139, US-A-4028643, US-A-4463330, US-4677404.

References

Informative references

Attention is drawn to the following places, which may be of interest for search:

Balun: Device which transforms a balanced input transmission signal to unbalanced output signals, are widely used in many application, such as balanced push pull amplifiers (H03H), antenna feed networks (H01Q) and double-balanced mixers.

Marchand Balun: see IMDT XP001178439

The Marchand balun (see figure below) includes a first line having a length that is one half of a wavelength corresponding to an operating frequency, a second line and a third line each having a length that is one quarter of the wavelength corresponding to the operating frequency, an input terminal connected to one end of the first line, an output terminal connected to one end of the second line, and an output terminal connected to one end of the third line. The output terminals operate in pair as differential output terminals.

Directional couplers are four-port circuits where one port is isolated from the input port. All four ports are (ideally) matched, and the circuit is (ideally) lossless.

What do we mean by "directional"? A directional coupler has four ports, where one is regarded as the input, one is regarded as the "through" port (where most of the incident signal exits), one is regarded as the coupled port (where a fixed fraction of the input signal appears, usually expressed in dB), and an isolated port, which is usually terminated. If the signal is reversed so that it enter the "though" port, most of it exits the "input" port, but the coupled port is now the port that was previously regarded as the "isolated port". The coupled port is a function of which port is the incident port.

Looking at the generic directional coupler schematic above, if port 4 is the incident port, port 3 is the transmitted port (because it is connected with a straight line). Either port 1 or port 2 is the coupled port, and the other is the isolated port, depending on whether the coupling mode is forward or backward.

Lange couplers are generally used to couple electromagnetic energy between transmission lines. In a four port hybrid, there is an input port and a direct port, these two ports being directly and conductively connected to each other, as well as a coupled port, the latter being connected to transmission lines coupled electromagnetically (inductively and capacitively) to the conductors extending between the input and direct ports.

In a Lange type coupler, each strip conductor is divided into mutually parallel sections, and the conductor sections from the two different strip conductors are interdigitated, so that each strip section is located between two sections from the other conductor. In a planar arrangement, it is necessary to have cross-over connectors in order to establish a direct conductive connection between the various sections extending in parallel.

The diagram above depicts a simplified version of the Magic T waveguide junction with its four ports.

To look at the operation of the Magic T waveguide junction, take the example of when a signal is applied into the "E plane" arm. It will divide into two out of phase components as it passes into the leg consisting of the "a" and "b" arms. However no signal will enter the "H plane" arm as a result of the fact that a zero potential exists there - this occurs because of the conditions needed to create the signals in the "a" and "b" arms. In this way, when a signal is applied to the H plane arm, no signal appears at the "E plane" arm and the two signals appearing at the "a" and "b" arms are 180° out of phase with each other.

Magic T waveguide junction signal directions

When a signal enters the "a" or "b" arm of the magic T waveguide junction, then a signal appears at the E and H plane ports but not at the other "b" or "a" arm as shown.